Clear cell renal cell carcinoma (ccRCC) is the most common form of kidney cancer and is often linked to loss of chromosome 3p, which harbors the VHL tumor suppressor gene, loss of chromosome 14q, ...which includes HIF1A, and gain of chromosome 5q. The relevant target(s) on chromosome 5q is not known. Here, we show that 5q amplification leads to overexpression of the SQSTM1 oncogene in ccRCC lines and tumors. Overexpression of SQSTM1 in ccRCC lines promoted resistance to redox stress and increased soft agar growth, while downregulation of SQSTM1 decreased resistance to redox stress, impaired cellular fitness, and decreased tumor formation. Therefore, the selection pressure to amplify 5q in ccRCC is driven, at least partly, by SQSTM1.
•Copy number gains of chromosome 5q drive SQSTM1 overexpression•SQSTM1 gene product p62 activates NRF2 and promotes resistance to redox stress•mTOR acts downstream or parallel of p62 in renal cancer cells•p62 promotes renal cancer growth in vitro and in vivo
Small cell lung cancer (SCLC) accounts for 15% of lung cancers and is almost always linked to inactivating
and
mutations. SCLC frequently responds, albeit briefly, to chemotherapy. The canonical ...function of the
gene product RB1 is to repress the E2F transcription factor family. RB1 also plays both E2F-dependent and E2F-independent mitotic roles. We performed a synthetic lethal CRISPR/Cas9 screen in an
SCLC cell line that conditionally expresses
to identify dependencies that are caused by RB1 loss and discovered that
SCLC cell lines are hyperdependent on multiple proteins linked to chromosomal segregation, including Aurora B kinase. Moreover, we show that an Aurora B kinase inhibitor is efficacious in multiple preclinical SCLC models at concentrations that are well tolerated in mice. These results suggest that RB1 loss is a predictive biomarker for sensitivity to Aurora B kinase inhibitors in SCLC and perhaps other
cancers. SIGNIFICANCE: SCLC is rarely associated with actionable protooncogene mutations. We did a CRISPR/Cas9-based screen that showed that
SCLC are hyperdependent on
, likely because both genes control mitotic fidelity, and confirmed that Aurora B kinase inhibitors are efficacious against
SCLC tumors in mice at nontoxic doses.
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.
More than 90% of small cell lung cancers (SCLCs) harbor loss-of-function mutations in the tumor suppressor gene
The canonical function of the
gene product, pRB, is to repress the E2F transcription ...factor family, but pRB also functions to regulate cellular differentiation in part through its binding to the histone demethylase KDM5A (also known as RBP2 or JARID1A). We show that KDM5A promotes SCLC proliferation and SCLC's neuroendocrine differentiation phenotype in part by sustaining expression of the neuroendocrine transcription factor ASCL1. Mechanistically, we found that KDM5A sustains ASCL1 levels and neuroendocrine differentiation by repressing NOTCH2 and NOTCH target genes. To test the role of KDM5A in SCLC tumorigenesis in vivo, we developed a CRISPR/Cas9-based mouse model of SCLC by delivering an adenovirus (or an adeno-associated virus AAV) that expresses Cre recombinase and sgRNAs targeting
, and
into the lungs of Lox-Stop-Lox Cas9 mice. Coinclusion of a KDM5A sgRNA decreased SCLC tumorigenesis and metastasis, and the SCLCs that formed despite the absence of KDM5A had higher NOTCH activity compared to
SCLCs. This work establishes a role for KDM5A in SCLC tumorigenesis and suggests that KDM5 inhibitors should be explored as treatments for SCLC.
Germline inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene causes the von Hippel-Lindau hereditary cancer syndrome, and somatic mutations of this gene have been linked to the ...development of sporadic hemangioblastomas and clear-cell renal carcinomas. The VHL tumor suppressor protein (pVHL), through its oxygen-dependent polyubiquitylation of hypoxia-inducible factor (HIF), plays a central role in the mammalian oxygen-sensing pathway. This interaction between pVHL and HIF is governed by post-translational prolyl hydroxylation of HIF in the presence of oxygen by a conserved family of Egl-nine (EGLN) enzymes. In the absence of pVHL, HIF becomes stabilized and is free to induce the expression of its target genes, many of which are important in regulating angiogenesis, cell growth, or cell survival. Moreover, preliminary data indicate that HIF plays a critical role in pVHL-defective tumor formation, raising the possibility that drugs directed against HIF or its downstream targets (such as vascular endothelial growth factor) might one day play a role in the treatment of hemangioblastoma and renal cell carcinoma. On the other hand, clear genotype-phenotype correlations are emerging in VHL disease and can be rationalized if pVHL has functions separate from its control of HIF.
Current systems for modulating the abundance of proteins of interest in living cells are powerful tools for studying protein function but differ in terms of their complexity and ease of use. ...Moreover, no one system is ideal for all applications, and the best system for a given protein of interest must often be determined empirically. The thalidomide-like molecules (collectively called the IMiDs) bind to the ubiquitously expressed cereblon ubiquitin ligase complex and alter its substrate specificity such that it targets the IKZF1 and IKZF3 lymphocyte transcription factors for destruction. Here, we mapped the minimal IMiD-responsive IKZF3 degron and show that this peptidic degron can be used to target heterologous proteins for destruction with IMiDs in a time- and dose-dependent manner in cultured cells grown ex vivo or in vivo.
Pharmacologic activation of the heterodimeric HIF transcription factor appears promising as a strategy to treat diseases, such as anemia, myocardial infarction, and stroke, in which tissue hypoxia is ...a prominent feature. HIF accumulation is normally linked to oxygen availability because an oxygen-dependent posttranslational modification (prolyl hydroxylation) marks the HIFα subunit for polyubiquitination and destruction. Three enzymes (PHD1, PHD2, and PHD3) capable of catalyzing this reaction have been identified, although PHD2 (also called Egln1) appears to be the primary HIF prolyl hydroxylase in cell culture experiments. We found that conditional inactivation of PHD2 in mice is sufficient to activate a subset of HIF target genes, including erythropoietin, leading to striking increases in red blood cell production. Mice lacking PHD2 exhibit premature mortality associated with marked venous congestion and dilated cardiomyopathy. The latter is likely the result of hyperviscosity syndrome and volume overload, although a direct effect of chronic, high-level HIF stimulation on cardiac myocytes cannot be excluded.
Loss of prolyl hydroxylase 2 (PHD2) activates the hypoxia-inducible factor-dependent hypoxic response, including anaerobic glycolysis, which causes large amounts of lactate to be released from cells ...into the circulation. We found thatPhd2-null mouse embryonic fibroblasts (MEFs) produced more lactate than wild-type MEFs, as expected, whereas systemic inactivation of PHD2 in mice did not cause hyperlacticacidemia. This unexpected observation led us to hypothesize that the hypoxic response activated in the liver enhances the Cori cycle, a lactate–glucose carbon recycling system between muscle and liver, and thereby decreases circulating lactate. Consistent with this hypothesis, blood lactate levels measured after a treadmill or lactate tolerance test were significantly lower inPhd2-liver-specific knockout (Phd2-LKO) mice than in control mice. An in vivo13C-labeled lactate incorporation assay revealed that the livers ofPhd2-LKOmice produce significantly more glucose derived from13C-labeled lactate than control mice, suggesting that blockade of PHD2 in the liver ameliorates lactic acidosis by activating gluconeogenesis from lactate.Phd2-LKOmice were resistant to lactic acidosis induced by injection of a lethal dose of lactate, displaying a significant elongation of survival. Moreover, oral administration of a PHD inhibitor improved survival in an endotoxin shock mice model. These data suggest that PHD2 is a potentially novel drug target for the treatment of lactic acidosis, which is a serious and often fatal complication observed in some critically ill patients.
The von Hippel-Lindau tumor suppressor gene (VHL), which resides on chromosome 3p25, is mutated or silenced in >50% of sporadic clear cell renal cell carcinomas. Germ-line VHL mutations give rise to ...VHL disease, which is characterized by an increased risk of blood vessel tumors (hemangioblastomas) and renal cell carcinomas. In this setting, VHL inactivation gives rise to premalignant renal cysts. Additional genetic alterations are presumably required for conversion of these cysts to renal cell carcinomas. Restoration of VHL function in VHL-/- renal cell carcinomas is sufficient to inhibit tumorigenesis in vivo. On the basis of these and other data, VHL appears to be a critical gatekeeper with respect to the development of renal cell carcinoma. The VHL gene product, pVHL, is the substrate recognition module of an E3 ubiquitin ligase that targets the hypoxia-inducible factor (HIF) for destruction in the presence of oxygen. Hypoxic cells, or cells lacking pVHL, accumulate high levels of HIF, which activates the transcription of a variety of genes, including vascular endothelial growth factor, platelet-derived growth factor B, and transforming growth factor alpha. We have demonstrated that inhibition of HIF is necessary and sufficient for tumor suppression by pVHL in renal cell carcinoma nude mouse xenograft assays. This provides a rationale for treating VHL-/- renal cell carcinoma with inhibitors of HIF or its downstream targets. Genotype-phenotype correlations in VHL disease suggest, however, that pVHL has targets in addition to HIF. Elucidating these targets should provide a more complete picture of how pVHL suppresses tumor growth.
Immune checkpoint inhibitors targeting the programmed cell death 1 receptor (PD-1) improve survival in a subset of patients with clear cell renal cell carcinoma (ccRCC). To identify genomic ...alterations in ccRCC that correlate with response to anti-PD-1 monotherapy, we performed whole-exome sequencing of metastatic ccRCC from 35 patients. We found that clinical benefit was associated with loss-of-function mutations in the
gene (
= 0.012), which encodes a subunit of the PBAF switch-sucrose nonfermentable (SWI/SNF) chromatin remodeling complex. We confirmed this finding in an independent validation cohort of 63 ccRCC patients treated with PD-1 or PD-L1 (PD-1 ligand) blockade therapy alone or in combination with anti-CTLA-4 (cytotoxic T lymphocyte-associated protein 4) therapies (
= 0.0071). Gene-expression analysis of PBAF-deficient ccRCC cell lines and
-deficient tumors revealed altered transcriptional output in JAK-STAT (Janus kinase-signal transducers and activators of transcription), hypoxia, and immune signaling pathways.
loss in ccRCC may alter global tumor-cell expression profiles to influence responsiveness to immune checkpoint therapy.
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